The field of multimedia communications is burgeoning. As a result there is an increased demand for systems capable of efficiently encoding video signals. Dedicated hardware video encoders are becoming available. However, there remains a need for practical software-based video encoders based upon general purpose computer processors or digital signal processors. One challenge faced in designing software-based video encoding systems is that such software-based systems may be used on computer systems which have various levels of processing power. The system may provide acceptable performance when run on some computers but provide unacceptable performance on computers which have less computational resources available for use by the system.
Various standards for video coding have been promulgated. These include the MPEG-2 standard (formally known as ISO/IEC 13818) and the H.263 standard. The MPEG-2 standard applies to decoders and defines the characteristics of a byte stream representing a compressed video signal that can be successfully decoded by MPEG-2 decoders. Such coding standards have been used successfully to encode video in teleconferencing systems, digital television broadcasting, computer games, closed circuit television security applications and digital versatile disks (DVDs). These standards provide encoding methods which involve motion estimation (ME), motion compensation (MC), discrete cosine transformation (DCT), quantization and variable length coding (VLC). Some of these tasks are computationally intensive. Motion estimation, motion compensation and performing DCT operations are particularly computationally intensive.
The MPEG-2 and H.263 standards assume that the value of a particular pixel (pel for short) in an image can be predicted from the values of nearby pels within the same frame (using intra-frame coding techniques) or from the values of pels in a nearby frame (using inter-frame techniques). Current video encoding methods typically divide each video frame into a number of macroblocks. For each macroblock a motion vector is obtained. The motion vector indicates a location relative to the macroblock which contains pels having values similar to the pel values in the macroblock. After the motion vector has been obtained, residual data, representing the difference between pels in the location identified by the motion vector and pels in the macroblock is encoded. In most current video encoders DCT is used for encoding the residual data.
There is a need for methods and systems for video encoding which are more versatile than currently available methods and systems. There is a particular need for such systems and methods which can be readily adapted for use on various hardware.